The CN GP38s fall into three main groups:
4700-4732: These are road units with narrow nose cabs. All are equipped to lead.
4760-4810: These are road units with wide nose cabs. All are equipped to lead.
7500-7532: These are hump mother units used with the 5xx series of slugs. Sometimes these are seen with a single GP38 and a single slug, or sometimes in a GP38-slug-slug-GP38 configuration. Even numbered ones are equipped to lead; odd numbered ones are used only in the trailing position. Some are equipped for remote control operation (the white cone antennas above each side the cab are indicators of this).